1. Field
Exemplary embodiments of the present invention relate to a nonvolatile memory device and a method for fabricating the same, and more particularly, to a 3D nonvolatile memory device including a plurality of memory cells stacked perpendicular to a surface of a substrate and a method for fabricating the same.
2. Description of the Related Art
A nonvolatile memory device maintains data stored therein although power is turned off. Currently, various nonvolatile memory devices, such as a flash memory, are widely used.
In particular, as the improvement in the degree of integration of 2D nonvolatile memory devices, including a plurality of memory cells formed in a single layer over a semiconductor substrate, approaches the limits, a 3D nonvolatile memory device, including a plurality of memory cells formed along a channel layer protruding perpendicularly from a surface of a semiconductor substrate, has been proposed.
FIG. 1 is a cross-sectional view of a conventional 3D nonvolatile memory device.
Referring to FIG. 1, the 3D nonvolatile memory device may include a word line WL extending in one direction while surrounding a channel layer CH protruding vertically from a substrate.
Although not illustrated in FIG. 1, the word line WL may be formed by the following process: a plurality of sacrificial layers are removed from a structure in which a plurality of interlayer dielectric layers and the plurality of sacrificial layers are alternately stacked along the channel layer CH. A conductive material is deposited to such a thickness as to fill the space from which the sacrificial layers is were removed, and an etching process for etching the deposited conductive material for the respective layers is performed. At this time, line or dot-shaped voids may be formed in the word line WL, and may serve as a factor that increases the resistance of the word line WL.
In particular, during the etching process, the conductive material is further etched at a top word line WL than a bottom word line WL. Therefore, the top of the word line WL is formed to have a smaller volume than the bottom of the word line WL. Accordingly, the top of the word line WL has a relatively large resistance value. Furthermore, the conductive material may be excessively etched to open the word line WL (refer to symbol A), or the resistance of the word line WL may rapidly increase (refer to symbol B). Therefore, there is demand for the development of a structure capable of solving such concerns.